a nonparametric test, used when data are rank ordered, to determine whether two independent samples have been drawn from the same population, on the basis of a comparison of their median values. It combines the Mann–Whitney U test and Wilcoxon rank-sum test into a single statistical procedure. [Frank Wilcoxon (1892–1965), Irish-born U.S. statistician; Henry Berthold Mann (1905–2000), Austrian-born U.S. mathematician; Donald Ransom Whitney (1915–2001), U.S. statistician]